Purifying art



Patented eb. 14, 1933 UNITED. STATES PATENT OFFICE IRVING D. HUBBELL,01' SAN FRANCISCO, CALIFORNIA, ASSIGNOR T SILICA GOMPAN'Y OF CALIFORNIA,LTD, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF GALI- roam PURIFYINGART Io Drawing.

This invention relates to the purification of silica sand, which iscontaminated with iron and perhaps other impurities.

oxide, etc., which is intermixed with thesand or forms a coating on thegrains there'- of. Silica is used in a great many processes and in themanufacture of various products; and the impurities therein frequentlyare undesirable in View of the manner in which they affect the processor color the product.

I have discovered that the impurities, for example such as the iron, maybe removed from the sand by suitable treatment with sulphur dioxide, asfor example, by dissolution ontreatment with an aqueous solution ofsulphuric acid containing sulphur dioxide, or by treatment with anaqueous solution of sulphur dioxide alone. The iron can thus be removedfrom the sand to such an extent as to make such sand much more valuablefor use in various processes for making various products, including themanufacture of soluble silicates, the manufacture of ordinary glass,etc.

Some of the iron can be removed by treating the silica sand withsulphuric acid of strength, but the use of acid of such strength isexpensive and uneconomical on account of the acid losses due tosubsequent washing, etc.

I have discovered that substantially all the iron can be removed fromthe silica send by treating it With a weak aqueous solution of sulphuricacid, for example, a solution containing 10% or less of sulphuric acid,and containing about 2% more or less otsulphur dioxide, and that thistreatment can be carried out very economically without the necessity ofapplying heat in the process, so that the treatment can be practiced inthe cold, thus saving the expense of heating means and material.

I have also discovered that the iron can be substantially all removedfrom the sand by proceeding in a similar manner, brt using an aqueoussolution containing about l%, or even less, of sulphur dioxidecontaining no sulphuric acid.

Application filed larch 4; 1930. Serial No. 433,184.

I have discovered further that my process can be carried out veryefliciently by providing a number of piles of sand to be treated,pouring the treating solution through one of the piles of sand, and whenthis solution has percolated through this one pile, it is poured onto asecond pile, and after percolation therethrough, it is poured onto a.third pile, etc. New treating solution may in the meanwhile be pouredonto the first pile and then through the second and third piles, the

treating solution being used on consecutive piles of sand until it isexhausted. By this means I treat stationary piles of sand practicallyonthe countercurrent principle, the pile of sand containing the least ironthus icing treated with the freshest treating solution. After pouring itnew or artiaily exhausted treating solution throng a pile of sand, Iprefer to let such pilestand without further treatment for a period ofabout (3 to 2% hours before treating with further solution, as thispermits access of air thereto which seems to have a beneficial efi'ecton the process.

The number oi treatments necessary will vary, of course, with the natureof the impurities present, and should be determined by analysis of thesand at different stages of r atment to formulate rule for sand from aparticular source, For sand of one particular source I have "found thatit) treatments at the rate of one a day are more than suficient.

My process is applicable to the treatment of other materials than silicasand, such as kaolin, clay, barytes, feldspar, as well as othermaterials; and it is applicable also to the removal of any impuritieswhich are dissolved by the treating solutions used.

Having thus described my invention, what I claim and desire to secure byLetters Patent of the United States is 1. The process of removingcontaminating iron from sand which comprises treating piled sand with anaqueous solution of sulphuric acid of-not over 10% strength COKE",taining sulphur dioxide.

2. The process of removin contaminating iron from sand which comprisestreating till sq ieous solution of sul- O siI-"engih containing about Tside. treating silica sand coniron to remove the iron therecoinp isesarranging said send stationary piles, pouring & Week sulphur dioxidethrough one of then ihrough another of said oouring another similarsolution aid first-mentioned pile and then mend-mentioned bile, wherebyasked with said so ution on the spplied to each pile. ss oi treatingsilica sand coniron to remove she iron ehereiieh comprises arrangingsaid send 5 of stsiionery piles, pouring 2: Weak ion of sulphur dioxideand $111 huric 'ihi'eugh one of said piles an then ugh enother of saidpiles, and pouring 1 solution through said firstend then through saidsecondpile whereby said sand is treateii solution on thecounier-cui'rent W ile the send is stationary, and al- 195i of about sixto "sW-entyiour o seiween the treatments up- 1:1 5. JBBELTL.

